A composite cable including an optical fibre cable and an electric power cable may for example be used in offshore applications, such as submarine power and/or communication cables. Another example is installation environments that require monitoring of the operation of electricity, wherein the optical fibre cable may be used for detecting temperatures of the electric power cable. The optical fibre cable may comprise one or a plurality of parallel optical fibres and the optical fibre cable may comprise a tube in which optical fibre/-s is/are accommodated and protected. The optical fibre is used for fibre-optic communication and may thus send data along the composite cable. An optical fibre cable including a tube, e.g. made of a metal material, which houses one or a plurality of optical fibres, may be called an FIMT, Fibre in Metal Tube. The composite cable may be called a composite power cable.
Two composite cables or two cable ends often need to be connected to one another, for example when installing the composite cables in the application at hand, or in a jointing process if the cable is broken and requires repair. Also, in a continuous composite power cable, two optical fibre cables may need to be jointed in case of fibre break or fibre cable damage. In general, when jointing the optical fibres of two optical fibre cables, which may extend after one another along the axial extension of the composite cable, a certain extra optical fibre length has to be added in order to accomplish the jointing of the optical fibres of two optical fibre cables. In general, the electric power cable of the composite cable comprises one or a plurality of electrical conductors, e.g. three, and a circumferential cover located outside of the electrical conductor/-s. The cover may be armouring, or an armouring cover, provided to protect the elements of the composite cable located within the armouring. The cover may also be a circumferential conductive screen located outside of a circumferential electrically insulating layer which in turn is located outside of the electrical conductor, wherein the screen is arranged to be held at ground potential. The composite cable may also comprise a circumferential outer jacket, e.g. made of polymer material, located outside of the cover and of the electrical conductor in order to provide further protection. The composite cable may comprise additional layers or jackets of different materials, e.g. an additional circumferential electrically insulating layer.
In general, the optical fibre cable is located inside of the outer jacket or embedded within or located inside of the cover. Often, the armouring, or armouring cover, is formed by a plurality of parallel longitudinal wires in one or a plurality of layers in the radial direction. When producing a composite cable having wire armouring, the wires are applied close to one another along the longitudinal extension of the cable, generally along helical lines. One or a plurality of the wires may be replaced by an optical fibre cable, whereby the optical fibre cable requires no additional space inside of or outside of the armouring. After the production of the composite cable, when jointing two already manufactured composite cables or repairing a defective composite cable, two optical fibres or two optical fibre ends of two optical fibre cables may need to be jointed. However, since the optical fibre cable is embedded in the composite cable and essentially axially immovable, e.g. by being located inside of the jacket or even inside of the armouring, or by being embedded in and being part of the cover, e.g. the armouring, as described above, extra optical fibre length needs to be added to be able to joint two optical fibres. The extra optical fibre length is often needed because of the equipment used for jointing optical fibres, e.g. a fusion splicing apparatus, which requires a space between the optical fibre cable and the remainder part of the composite cable. After completion of the splicing of the optical fibres, an overlength of optical fibre remains, i.e. an extra optical fibre length. This optical fibre overlength has to be dealt with and protected from the exterior environment outside of the composite cable. The optical fibre overlength may also take up space or room such that the outer dimension of the composite cable is increased, which may be a disadvantage. An optical fibre cable may also be sensitive to harsh bending, which should be considered when taken care of the extra optical fibre length.
In prior art there are examples of how to take care of the extra optical fibre length created when jointing optical fibres of a composite cable.
US 2012/0033928-A1 discloses a cable joint for jointing two cable ends of an optical fibre cable of an optical fibre composite electric power cable. The cable joint includes a repair box having storage for storing extra length needed for jointing fibres of the optical fibre cable.
CN 101719651-A describes a composite power cable connection box used for an optical fibre arranged in the centre of a conductor.
EP 0 646 817-A2 discloses means for jointing a bundle of longitudinal elements, such as a composite electrical/fibre optic cable. A jointing compartment for the fibres is provided where jointing can be undertaken.
JP 59212813-A describes a connection part of a power cable containing optical fibre.
U.S. Pat. No. 6,281,431-B1 discloses a cable joint for a multi-core cable including an outer sheath surrounding at least one electric pilot line and/or at least one optical fibre line and/or tube therefore.
CN 201917691 describes a fibre optics attachment structure for connecting the fibre optics in heterogeneity electricity optical fibre compound power cable.